1. Technical Field
The present invention generally relates to a method of forming a via in a substrate, and more particularly, to a method for forming a via in a substrate using a support.
2. Background Art
In the production of substrates, such as printed wiring boards or laminated chip carriers, the formation of vias, through holes, or the like is often necessary. As such, various drilling methods are employed. However, a problem exists when the vias are formed in that the entry and exit portions of the vias are often left distorted by the drilling operation. In addition, debris from formation of the vias remains disposed along the entry and exit portions of the vias. This debris is not only adverse to the performance of the substrate, but is also time consuming and costly to remove. Although a number of methods of forming such vias exists, no previous method eliminates these problems, hereinafter referred to as "volcanoing."
Heretofore, many have attempted to develop suitable methods of forming vias, but have fallen short. One such example of this is shown in Japanese Publication No. 58218387 JP A1, in which plastic powder is packed as a backing material on a workpiece as a laser drills a hole therethrough. However, because the plastic powder is not laminated to the workpiece, additional components, such as a piston, are necessary to maintain the contact between the backer and the workpiece. In addition, the plastic powder does not aid in the removal of the debris generated from drilling the workpiece. In contrast, upon removal of the plastic powder, the debris is still present on the workpiece.
Another example of a backing material is shown in Japanese Publication No. 58058987 JP A1, which teaches the use of a metallic plate as a backer material. Specifically, a metallic plate is closely adhered to a workpiece which is then pierced by a laser to form holes therein. By, adhering a metal plate to the workpiece, however, additional process steps are required to remove the backing plate. Moreover, the rigid nature of a metallic plate fails to collect the debris created from drilling the workpiece, thus, leaving the debris disposed along the surfaces of the workpiece.
Yet another example of a backer material is shown in Japanese Publication No. 59033091 JP A1, which teaches the contact of a "plate-like" object into tight contact with a workpiece. Once tight contact is achieved, the workpiece can then be laser drilled to form holes therethrough. Similar to the above reference, however, the use of a plate-like object not only requires additional process steps for removal, but also fails to remove the debris generated by the drilling operation.
Lastly, U.S. Pat. No. 4,857,698 to Perun, herein incorporated by reference, teaches the use of an adhesive tape as a backer material. In particular, Perun shows an adhesive tape that is adhered to an article which is then drilled to form holes therein. However, the use of adhesive tape can be costly, and its removal can result in structural damage to a workpiece, especially if the workpiece is thin and lightweight. In addition, the removal of residue from the tape adhesive requires additional processing steps.
Therefore, there exists a need for a support material, hereinafter referred to as a "support," that can be used in the formation of vias or the like, such that the entry and exit portions of the vias are evenly formed (not distorted). In addition, there exists the need for a support that will remove any debris generated by the drilling operation from the workpiece surface upon removal of the support.